An internal combustion engine (engine) extracts work from a combusted mixture of fuel and air. In one common form, an engine includes one or more reciprocating pistons that drive a crankshaft. The pistons are slide-ably disposed within cylinders formed in a cylinder block. A cylinder head is secured to the cylinder block so as to provide a controllably sealable chamber for the compression, combustion, and expansion of the mixture of fuel and air. The cylinder head defines a combustion chamber for each cylinder above the top of the respective piston. The cylinder head also defines passages for the intake of air and fuel into each cylinder and for the discharge of combustion products from each cylinder.
As each of the pistons reciprocates within its respective cylinder, it proceeds through a series of strokes including an intake stroke, during which the respective cylinder receives a supply of combustible fuel and air, and an exhaust stroke, during which expanded products of the combusted fuel and air mixture are discharged from the cylinder.
An intake manifold provides intake runners for carrying the supply of air (and, optionally, combustible fuel) to each intake passage of the cylinder head. An exhaust manifold carries discharged products of combustion from the exhaust passages of the cylinder head. The exhaust manifold gathers exhaust gases from the various exhaust passages of the cylinder head, carries the exhaust gasses through a set of corresponding exhaust runners, and collects them into a single stream of exhaust gas. The exhaust manifold is typically a separate component coupled to the cylinder head with threaded fasteners. The exhaust manifold routes the gases toward the catalysts and mufflers of the exhaust system.
Frequently, the cylinder head is detachable from the top of the engine and contains spark plugs and the intake and exhaust valve openings associated with each of the cylinders of the cylinder block. In some embodiments, the cylinder head also contains one or more fuel injectors for injecting fuel into respective cylinders and a camshaft for opening and closing the intake and exhaust valve openings during appropriate time intervals. The cylinder head and cylinder block may include a series of coolant passages that facilitate circulation of coolant. Coolant is circulated through the coolant passages within the cylinder block and the cylinder head to extract heat, particularly from the vicinity of the cylinders, the combustion chamber and the valve-train components.
Environmental sustainability, increasing global energy demand, increases in energy costs, and increasing demand for independent, cost-effective transportation is driving vehicle and power-train designers to produce smaller and more fuel-efficient vehicles. Thus, inline engines with only three or four cylinders are increasingly being used to power medium to small sized vehicles. At the same time, the inline cylinder configurations commonly used for such engines tend to define minimum vehicle space requirements for packaging the engines. As a result, narrow-angle, V-configured engines are increasingly being considered due to the packaging advantages they offer. By staggering pistons in offset banks, V-configured engines offer additional pistons (and power) without unnecessarily increasing engine length. Unfortunately, engine height may suffer in such engines due to the use of a single cylinder head with a height beyond that required for an inline engine.
Accordingly, as engine manufacturers continuously strive to improve engine operating efficiency and to reduce manufacturing costs, it is desirable to have engine configurations and components offering improved operating efficiencies, improved packaging compactness, improved cooling effectiveness, and reduced cost.